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Re: Alternative to 303 response: Description-ID: header

From: Ian Davis <lists@iandavis.com>
Date: Wed, 05 Dec 2007 15:55:14 +0000
To: Tim Berners-Lee <timbl@w3.org>
Cc: "Sean B. Palmer" <sean@miscoranda.com>, David Booth <dbooth@hp.com>, www-tag@w3.org
Message-Id: <1196870114.15636.18.camel@iand-laptop>


On Wed, 2007-12-05 at 10:31 -0500, Tim Berners-Lee wrote:
> Ian,
> 
> Your blog says, in http://iandavis.com/blog/2007/12/303-asymmetry
> 
> 
> 'Suppose I have a resource “R” with URI http://example.org/R. If it is  
> an “Information Resource” then I can arrange things so that a GET  
> request for its text/html representation responds with a 200 and the  
> HTML in the body of the response. I could also arrange for a request  
> for its application/rdf+xml representation to respond with a 303  
> status and the URI of another information resource “RDESC” (e.g. http://example.org/RDESC) 
> . In this example the 303 response meand that “R” cannot be  
> represented as RDF, but there’s an alternative RDF document that is a  
> description of R."
> 
> There is a major problem with this, though.   Content negotiation is  
> just for different encodings of the

> On 2007-12 -04, at 20:56, Ian Davis wrote:
> 
> >
> > On Tue, 2007-12-04 at 19:53 -0500, Tim Berners-Lee wrote:
> >>
> >> I did wonder about the following:  in the case when the URI is not of
> >> document, when currently we use 303,
> >> then the  server can return a document *about* it with  an extra
> >> header to explain to the browser
> >> that it is actually giving you a description of it not the content of
> >> it.  (Pick a header name)
> >
> >
> > Strange synchronicity... I posted the same idea a few minutes ago to  
> > my
> > blog:
> >
> > http://iandavis.com/blog/2007/12/303-asymmetry
> >
> > I called my header "resource-description"
> >
> > Ian
>  SAME document.
> You can content negotiate between PNG and JPG of the SAME picture.
> Between text/plain and text/html of the SAME document.
> Between RDF/xml and N3 of the SAME data.
> 
> You cannot use conneg to return a completely different document, eg  
> not A but  metadata bout A.
> A and A' must carry exactly the same information, module an  
> 'acceptable' degree of degradation.
> 
OK. But in my blog post I'm not suggesting returning both RDF and HTML
via conneg. I'm saying that you could return HTML for the information
resource and a 303 when asked for an RDF representation, meaning the
server doesn't have one but see this other document instead.


> When people conneg between HTML and RDF, the HTML is generated from  
> the RDF. Else it is  a bug.

I think there's still a clash of fragment identifier semantics even in
this case... but that's a different issue.


> 
> You say, "How can I allow the user to obtain a description of RDESC?  
> The representation I send back is the content of RDESC, not its  
> description. I can’t use the media type to distinguish the type of  
> request any more."
> Sorry, you never could.
> 
> The resource-description header you suggest seems very similar to teh  
> HHP link header, Link: foo.rdf; rel=meta
> (se http://esw.w3.org/topic/LinkHeader)

Yes. We better hurry up and get the link header through the ietf - there
are more and more uses for it every day :)



> Tim
> 
> 

Ian
Received on Wednesday, 5 December 2007 15:57:28 GMT

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